FIG. 1 is a schematic structural diagram of a conventional touch panel. As shown in FIG. 1, the conventional touch panel includes a common electrode layer Comm, which is provided with multiple electrode blocks E insulated from each other, and each of the electrode blocks E may serve as a common electrode and a touch electrode, that is, the common electrode doubles (is also used) as the touch electrode in the conventional touch panel. Each of the electrode blocks E is connected to a signal line 10, and the signal line 10 is configured to transmit a common voltage signal and a touch sensing signal to the electrode block E connected to the signal line 10 in a time-division manner.
FIG. 2 is a schematic structural diagram of a circuit for one pixel unit in one electrode block. An electrode block 200 includes multiple pixel units, and each pixel unit is provided with a TFT transistor and a pixel electrode. A gate of the TFT transistor is connected to a gate line G, a source of the TFT transistor is connected to a data line D, and a drain of the TFT transistor is connected to the pixel electrode.
The touch panel with the common electrode doubling as the touch electrode is driven in a time-division manner, that is, a display drive operation is performed before a touch drive operation is performed in one frame.
In the case that the touch panel is in a display period, the TFT transistor for controlling the pixel unit is turned on, a data signal is transmitted to the pixel electrode via the data line D, and a common voltage signal is transmitted to the electrode block 200 via the signal line 10; and in the case that the touch panel is in a touch sensing period, a touch sensing signal is transmitted to the electrode block 200 via the signal line 10. Whether the touch panel is in the display period or the touch sensing period, a pixel capacitor comprised of the pixel electrode and the common electrode is charged. Hence, while the touch panel is operating, there is a potential difference between the pixel electrode and the common electrode corresponding to the pixel electrode, and thus the liquid crystal molecules between the pixel electrode and the common electrode are twisted with a specific angle. In the case that the touch screen is suddenly powered off, the pixel capacitor is not discharged or partially discharged, and thus there is an amount of residual charge between the pixel electrode and the common electrode in a long term. The liquid crystal molecules may not be twisted due to the existence of the residual charge. Furthermore, some impurity ions in the liquid crystal may be polarized and the polarized impurity ions may not be twisted due to the presence of the residual charges, and the polarized impurity ions may be attached to an upper substrate and a lower substrate of the touch screen due to the presence of the residual charge in a long term. Noticeable flickers may occur on a touch screen when the touch screen is turned on.